Method and device for controlling a pump of a brake system

ABSTRACT

The present invention relates to a method and device for driving a brake system pump motor, which has the advantage of simultaneously allowing prioritized, individual braking strategies, using the present invention as a subsystem for intelligently driving the pump motor. The invention provides the additional advantage of reducing pump motor current requirements, allowing the use of a reduced size of pump motor. The invention provides for a predetermined period of full-on voltage at the initiation of a braking request, subsequent periods of variable pump motor voltage on-time, depending on pulse width modulation of a drive motor signal based on a comparison between the motor voltage and a threshold voltage, and subsequent periods of full-on voltage for a predetermined period based on a comparison between the motor voltage and a safety threshold voltage.

This is a continuation of application Ser. No. 09/552,867 filed Apr.20,2000 now U.S. Pat. No. 6,499,813

BACKGROUND INFORMATION

The present invention relates to a method and device for controlling apump of a brake system, such as in an anti-skid control system, afriction control system, or a vehicle dynamics control system accordingto the preambles of the independent claims.

German Patent Application 42 32 130 A1 describes a method and a devicefor controlling an electric motor-driven hydraulic pump that is used togenerate the servo pressure of a brake system with anti-skid controland/or traction control. For this purpose, it is driven with a variabledrive cycle composed of a pulse/pause sequence. The voltageregeneratively induced by the pump motor in the interpulse pauses isevaluated as a measure of pump speed. The computed difference betweenthis generator voltage as an actual speed quantity and a setpointquantity for the pump motor speed formed in an anti-skid control ortraction control system provides a differential quantity to a downstreamcontroller. The pulse width-modulated actuating signal for driving thepump is formed with the output signal from the controller. The drivemotor of the hydraulic pump is turned on and off with the clock pulse ofthis pulse width-modulated actuating signal.

It has been shown that the known method and corresponding device areunable to provide optimum results in every respect. The object of thepresent invention is therefore to provide an optimized method that canalso offer the driver a comfortable pedal sensation independently of thesetpoint quantity formation, at the same time providing a simple controlstructure.

To this end, German Patent No. 198 18 174, which is not a priorpublication, shows a method for controlling a pump of a brake system, inwhich a pump is initially connected to the voltage supply for aspecifiable period of time, in response to a pumping request in a brakesystem. Subsequently, the pump then receives at least one controlsignal, which is constant for at least one time interval and is formedfrom the sum of the pulse duration and interpulse period. In this drivecycle, a drive pulse for switching the pump on again is generated basedon a comparison of a motor voltage to threshold voltage values.Consequently, the starting pulse for the pump is not generated until aload occurs, which is characterized by the motor voltage reaching athreshold voltage value. Preventive recognition of a load situation andintensified driving of the pump resulting from this, are not shown. Inaddition, this document only starts with an arbitrary control algorithmor a feedback control. The use and coordination of severalsimultaneously active feedback controls acting on the pump is not shown.

This object as well as additional improvements are achieved according tothe independent claims, with the method according to the presentinvention as well as the corresponding device.

ADVANTAGES OF THE INVENTION

Initially, the pump is not clocked and is driven at full load for aselected time TAnstMax, i.e., full supply voltage Ubat, in particular,is applied to the pump, driving the latter with a clocked PWM signalthat is derived from a direct comparison between motor voltage UM, whichdrops across the pump motor, and at least one selected voltage thresholdvalue Us. For safety reasons, a minimum on-time TPeinMin=TTakt−TPausMaxof the pump can be maintained within a drive cycle by a predeterminedmaximum off-time TPausMax. Also due to safety considerations, the pumpis driven at full load upon reaching a minimum voltage threshold Uss,i.e., supply voltage Ubat, in particular, is applied to the pump motorfor a certain period of time. By using motor voltage UM in a directcomparison with different voltage threshold values, the method can beused independently of the controller concept.

The method according to the present invention and the device having theindependent features of the claims, have the advantage that not only isthe equipment and methodological design simple, but they can be usedindependently of the brake logic (e.g., anti-skid control/tractioncontrol/vehicle dynamics control system). In addition, the forcedpumping action of the pump during drive cycle period TTakt produces adefined pedal sensation. This continuous availability of the activepressure variation in the brake circuit, due to minimum pump on-timeTPeinMin, is also secondarily relevant to safety. Defined minimum pumpon-time TPeinMin per clock cycle TTakt avoids what may be a largedifference between the existing pressure and the pressure needed in thebrake circuit, e.g., when a sudden pumping request is received from thebrake system. This makes it possible to maintain a low average speed ofthe pump motor, since the pump is additionally fully driven whensubjected to a heavy load, and consequently upon meeting certainconditions, in particular when motor voltage UM reaches a selectablesafety threshold voltage Uss. Using a variable number of thresholdvalues and different clock cycle times and/or driving times assigned tothem makes it possible to adapt the system to any braking situation. Thevariable pump on- and off-times advantageously make it possible toreduce the pump motor speed without sacrificing performance.

It is also advantageous for the pump motor voltage to drop to a valuethat is less than a further threshold voltage during normal clockingoperation, in which case this further threshold value can alsocorrespond to safety threshold Uss or another threshold voltage Us, thusreactivating the pump for the rest of the cycle, additionally increasingavailability.

If pump motor voltage UM drops to a value that is smaller than, forexample, safety threshold value Uss directly after the pump is turnedoff, i.e., during the next cycle, the pump is reactivated for aselectable period of time. By allowing pump motor voltage UM to dropimmediately after deactivation reveals that the pump is under heavy loadduring this phase. Consequently, the pump can be driven during thisphase for a time that is much longer than the drive cycle period. Thiscritical threshold, e.g., Uss, can be used to simultaneously prevent thepump motor from remaining at a standstill.

According to one advantageous embodiment, the method for driving thepump motor is designed so that the pump driving action according to onecontrol strategy, e.g., traction control, is independent of the pumpdriving action according to another control strategy, such as anti-skidcontrol. This can be accomplished by using different parameters anddifferent logic components for the control systems. Each controlstrategy, i.e., each control system—such as anti-skid control ortraction control—can intervene in pump motor clocking at any time,depending on certain input, e.g., using a flag. A priority controlsystem can also avoid additional pump driving conflicts. This enablesintervention to be made in the pump motor clocking at any time so thatthe pump is switched between continuous and full drive. This makes itpossible to provide a modular pump motor drive mechanism that uses onlyone algorithm or only one basic logic. In this module, independent pumpmotor clocking of the individual systems i.e., control arrangementsinfluencing the braking action can be operated simultaneously to ensurevehicle driving stability and/or safety.

Further advantages lie in reducing the pump motor current andconsequently in dimensioning the pump motor, since it needs to be drivencontinuously only for a short period of time. The duration of full drivecan be limited by estimated wheel break pressures, especially whendecreasing from a high wheel pressure level.

A pump motor module can also be provided with an additional input for aflag. Controlled, for example, by the traction control algorithm, thisflag can be used to immediately disable clocking of the pump drivingaction, e.g., by the anti-skid control system, and the pump can bedriven in a different mode. The same also applies, of course, to allsystems i.e., control arrangements influencing the braking action toprovide vehicle driving stability and/or safety.

With the embodiments described above and the conditions selectedtherein, the pump can be driven selectively and optimized to itsrequirements and the current operating mode.

Further advantages are the object of the claims and the description

DRAWINGS

One embodiment of the present invention is illustrated in the drawingand explained in greater detail in the description below.

FIG. 1 shows a block diagram of a drive circuit.

FIG. 2 shows a flow chart illustrating a possible pump drive sequenceand

FIG. 3 shows signals of motor voltage UM and drive signal UP.

FIG. 4 shows a further embodiment of a method in the form of a flowchart in which, in addition to FIG. 2, multiple controllers arecoordinated and a pump is preventively driven on the basis of furtherconditions in addition to the voltage threshold query.

DESCRIPTION OF EMBODIMENTS

FIG. 1 and FIG. 2 show the ways in which the desired variation in thecontrol signal of the pump illustrated in FIG. 3 can be producedaccording to the present invention. Motor voltage UM of the pump motor,which is also illustrated in FIG. 3, serves as an input quantity. FIG. 3does not show negative voltage peaks that generally occur in motorvoltage UM immediately after the pump motor is turned on (for example,see German Patent Application 42 32 130 A1, FIG. 3), since the signal isalways evaluated only after these voltage peaks occur. FIG. 1 shows apossible drive circuit, and FIG. 2 shows a possible implementation of aprogram sequence in a control unit on the basis of a flow chart.

In FIG. 1, a pump motor 100 is connected to a supply voltage Ubat via aswitching means 107. On the switching means side of the pump motor, aconnection is established to two comparison means 101, 102. Furthermore,one comparison means 102 is connected to a line over which a voltagevalue Uss is supplied to comparison means 102 Likewise, a secondcomparison means 101 is connected to a line over which a second voltagevalue Us is supplied to comparison means 101. The output of comparisonmeans 102 is connected to an AND gate 110, and the output of comparison101 is connected to an AND gate 111. From controller 108, a line leadsto AND gate 110 and a second line to AND gate 111. The output of ANDgate 110 is connected to a holding element 104. The output of AND gate111 is connected to a holding element 103. A synchronization line alsoleads from a controller 108 to holding elements 103 and 104. Thissynchronization line is also connected to a pulse generator 105. Theoutputs of holding elements 103, 104 and pulse generator 105 areconnected to an OR gate 106. The output of this OR gate 106 leads toswitching means 107 and controls the latter. Switching means 107connects and disconnects pump motor 100 to and from a supply voltageUbat. The output of OR gate 106 additionally leads to controller 108.The pumping request is transmitted to controller 108 from asuperordinate logic, e.g., from a anti-skid control system, tractioncontrol system, or vehicle dynamics control system, via a line 109.

The operation of the circuit arrangement illustrated in FIG. 1 isdescribed below. Voltage UM that is present at the motor of pump 100 ofa brake system is tapped and supplied to two comparison means 101, 102.

In addition to using the analog quantities for motor voltage UM, UM mustbe input and prepared, e.g., for use in a computer program. To use motorvoltage UM according to the present invention, the information that itcontains is a determining factor and can be used as either analog ordigital information.

Motor voltage UM is compared in a comparison means 101 to a selectedfixed threshold voltage Us that is dependent, for example, on thevehicle type and/or brake system (arrangement, brake fluid volume,etc.). Likewise, motor voltage UM is compared in a second comparisonmeans 102 to a lower, but also fixed safety threshold Uss. The result ofthe comparison in comparison means 102, however, is evaluated onlyduring a first interval T1Max after the beginning of clock cycle TTakt.To do this, AND gate 110 is enabled by controller 108 only for thisfirst interval T1Max. During this first interval T1Max of clockingoperation, a check is also carried out to see whether UM drops belowthreshold voltage Us, after which gate 111 is also switched through.During subsequent sampling intervals dT of a clock cycle TTakt, i.e.,after T1Max, controller 108 enables only second AND gate 111. Duringfirst interval T1Max, therefore, the signals from comparison means 101and 102 are switched to holding elements 103 and 104. When motor voltageUM reaches safety threshold Uss during first interval T1Max, the signalproduced by this comparison in comparison means 102 is switched to ORgate 106 in holding element 104 for period of time TAnstMax. This setsswitching means 107 to the switching position in which it connects pumpmotor 100 to supply voltage Ubat for period TAnstMax. The pump is thusdriven at full load for period TAnstMax, which prevents the pump frombeing turned off at the end of the cycle. If UM does not reach Uss, butonly threshold voltage Us, during first interval T1Max of the clockingoperation, pump motor 100 remains connected to the voltage until the endof clock cycle TTakt after the comparison result is switched fromcomparison means 101 to holding element 103. Holding element 103 thusswitches this comparison result to OR gate 106 before the end of drivecycle TTakt. Switching means 107 is therefore set to the switchingposition in which it connects pump motor 100 to supply voltage Ubat forperiod TPein=TTakt−TPaus. Within a clock cycle TTakt, TPaus is the pumpoff-period which, in this case, ends when motor voltage UM reachesthreshold voltage Us. Holding elements 103, 104, can, for example, beimplemented by flip-flops, sampling and holding elements, etc. or byprogramming equivalents (see FIG. 2). A particularly importantconsideration in this regard is the fact that only the signal that isswitched from comparison means 101, 102 to elements 103, 104 via gates110, 111 when motor voltage UM reaches threshold Us or Uss is maintainedfor desired period TAnstMax or TPein, thus connecting pump motor 100 tosupply voltage Ubat for these periods of time. If threshold value Us orUss is not reached, the resulting comparison signal is not maintainedfor selected time TAnstMax or TPein. Together with the two signals fromholding elements 103 and 104, a third signal is supplied from a pulsegenerator 105 with an interpulse pause TPausMax to OR gate 106. In thisconnection, the pulse can also be generated by a frequency generator orsimilar device. Selected maximum pump off-time TPausMax begins withdrive cycle TTakt and ends before the end of this cycle. After timeTPausMax, the pulse generator switches a drive pulse to switching means107 via OR gate 106, maintaining this pulse until the end of drive cycleTTakt. This places switching means 107 into the switching position inwhich it connects pump motor 100 to supply voltage Ubat for periodTPeinMin=TTakt−TPausMax. This provides a minimum on-time TPeinMin ofpump motor 100 per drive cycle TTakt. The signal resulting from OR gate106 then controls switching means 107, which alternately establishes andinterrupts the connection between supply voltage Ubat and pump motor100. Both holding elements 103, 104 and pulse generator 105 havestarting times that are synchronized with the beginning of drive cycleTTakt, which coincides with the pump turn-off time. Controller 108 isused to provide full pump drive for TAnstMax at the beginning ofcontrol, to enable comparison means 101, 102 by enabling correspondingAND gates 110, 111, and to synchronize elements 103, 104, 105 connectedupstream from OR gate 106 with the drive cycle. The input quantitiesreceived by controller 108 include the signal from OR gate 106, whichalso controls switching means 107. Because of this, controller 108 knowswhen pump motor 100 is disconnected from supply voltage Ubat. This makesit possible to initiate drive cycle TTakt after pump motor 100 isdisconnected from Ubat, e.g., after a full drive phase for TAnstMax. Itis also conceivable to provide a counter in the controller instead of ortogether with this input signal, with this counter being used todetermine the pump turn-off time after full drive has been achieved.When the pump is at a standstill, the starting time for driving the pumpis a pump request, which also serves as the input signal for controller108 and comes from superordinate controller logic 109 (e.g., anti-skidcontrol/traction control/vehicle dynamics control system).

FIG. 2 contains a flow chart illustrating the pump drive sequence inthis particular embodiment.

In this case, the function of the drive circuit illustrated in FIG. 1 isimplemented by a programming equivalent, e.g., in a control unit. Inblocks 201, 211, 266, 216 a, and 204 of the flow chart, Pump ON and PumpOFF represent the alternate connection and disconnection of pump motor100 to and from supply voltage Ubat by an approximate switching means.The starting point is a pump request 200 from a superordinate logic forbuilding up pressure at the discharge end and decreasing pressure at theintake end, respectively. This program request 200 can be the result ofa detected wheel instability in the case of anti-skid control ortraction control as well as a detected vehicle instability in the caseof vehicle dynamics control and is signaled by a corresponding logic 109a. Pump request 200 thus establishes beginning of control 201 at whichpoint a counter for recording the time of full drive TAnst is reset.Full drive duration TAnstMax is also defined in 201. The counter is thenincremented 202 at intervals of sampling time dT, and the time conditionfor the maximum period of full drive TAnstMax is checked 203. Blocks 202and 203 in the flow chart correspond to the function of holding element104 in FIG. 1. After each sampling step, a check is carried out in block214/1 to see whether the pump request from block 200 is still present ornot. If the pump request is no longer present, the driving operation iscanceled and the pump turned off 216. This state is signaled tosuperordinate logic 109 a. Brief spurious signals do not cause thesystem to cycle through the entire driving sequence. This functionalityis exactly the same in blocks 214/1, 214/2, 214/3, and 214/4, the onlydifference being that these blocks are positioned elsewhere in the flowchart in FIG. 2. If the pump request is still active, the pump receivesfull drive during the first cycle. At the end of full drive timeTAnstMax, the pump is disconnected from power supply 204. This is thestarting point for drive cycle TTakt in the program and thesynchronization time for holding elements 102, 104 as well as pulsegenerator 105 in FIG. 1. In the drive circuit illustrated in FIG. 1, thepump can be turned on at beginning of control 201 by switching thecomparison result from comparison means 102 via gate 110, since pumpmotor 100 has not yet started up at this point, which means that motorvoltage UM is still below safety threshold Uss. In block 204 of FIG. 2,the counter variable for off-time TPaus of pump motor 100 is now reset,and drive cycle TTakt and maximum pump off-time TPausMax are defined perdrive cycle. The duration of drive cycle TTakt thus begins for the firsttime when pump motor 100 is disconnected from supply voltage Ubat. Basedon this initialization step 204, which is performed by controller 108 inFIG. 1, pump motor off-time TPaus as well as the period of firstinterval T1 are incremented by adding up sampling intervals dT in 207. Acheck to determine whether the drop in input motor voltage UM has causedthe latter to reach safety threshold Uss is carried out in 205 onlywithin first interval T1Max after pump motor 100 has been disconnectedfrom supply voltage Ubat. To do this, maximum length T1Max of intervalT1 is defined in block 208 prior to the first loop of the clockeddriving action, and counter variable T1 is reset for the interval. Acheck is carried out in block 206 to determine whether the sequence isin first interval T1 and thus whether a query 205 should be made to seewhether threshold Uss has been reached. After all, if motor voltage UMreaches safety threshold Uss during first interval T1Max, pump motor 100requires full drive according to the present invention, as required atthe beginning of control 201, 202, 203, and pump motor 100 must beconnected to supply voltage Ubat for period TAnstMax. Alternatively, adriving time TAnstMaxA that differs from TAnstMax, as shown by the areain FIG. 2 marked by dashed lines (201 a, 202 a, 203, 214/4, 216 a), canbe set for pump drive after UM reaches Uss. If UM does not reach Uss, acheck 209 of whether voltage threshold Us is reached is carried out,which corresponds to the signal sequence via comparison means 101 andgate 111 in FIG. 1; in addition a check 210 is carried out to seewhether TPaus has reached maximum pump off-time TPausMax. Thisguarantees minimum pump on-time TPeinMin=TTakt−TPausMax. This functionis performed by pulse generator 105 in FIG. 1. If UM has not reachedeither threshold Us or maximum off-time TPausMax, the pump motor remainsdisconnected from supply voltage Ubat. If one of conditions 209, 210 ismet, switching means 107 restores supply voltage Ubat of the pump motorin step 211. At the same time, a counter variable TPein is initialized,which can serve as a measure of the pump on-time, step 211. On-timeTPein is counted in a counter at sampling intervals dT, step 212, whichcorresponds to the function of holding element 103 in FIG. 1. Accordingto the present invention, pump on-time TPein, combined with off-timeTPaus should not exceed clock cycle duration TTakt despite guaranteedminimum on-time TPeinMin if the pump is driven by clocking. At themoment when clock cycle time TTakt is achieved by the addition of TPeinand Tpaus, step 213, The hydraulic pump is again disconnected fromsupply voltage Ubat. A PWM signal, which has the advantage of reducednoise development and also ensures greater reliability through theminimum on-time per clock cycle, is thus easily generated in the clockeddrive phase.

FIG. 3 now shows the resulting variation of motor voltage UM and pumpdrive signal UP, produced by OR gate 106 in FIG. 1. At beginning ofcontrol t0 (201), i.e., after a pump request 200 from superordinatelogic 109 and 109 a, respectively, full drive is achieved for durationTAnstMax (t1−t0). Full dive duration TAnstMax is permanently selected onthe basis of measured variables as a function, for example, of thevehicle type and/or the brake system used. The full drive phase ends atthe time the pump is turned off 204 following TAnstMax at t1. The pumpis then driven with selectable clock cycle TTakt (t2−t1) because, afterthe full drive phase, the full pump motor output is not necessary. Ifmotor voltage UM reaches threshold Us t4 (209), the pump is reactivatedfrom next sampling time t5 to the end of clock cycle TTakt at t6 (211,212, 213). Time difference t5−t4 between determining that thresholdvalue Us has been reached and activation of pump motor 100 is producedby sampling time dT used. If a hydraulic brake system now delivers brakefluid against a high pressure in the brake circuit, motor voltage UMdrops more quickly. If, however, brake fluid is delivered against alower pressure, motor voltage UM decreases more slowly. Differentturn-on times 211 of pump motor 100, produced by comparing the drop inmotor voltage UM (which takes place at different speeds) to selectedvoltage threshold Us, yield variations in on-durations TPein, thusmodulating the pulse width of drive signal UP. If, however, motorvoltage UM does not reach threshold Us (209), the pump remains on untilthe end of drive cycle TTakt t2 after expiration of the maximum pumpmotor off-time TPausMax t3−t1 (210). This yields minimum pump motoron-time TPein t2−t3 per drive cycle TTakt t2−t1. If motor voltage UMreaches safety threshold Uss T7 (205) directly after pump motor 100 isturned off, i.e., within first interval T1Max (208, 206), full drive t8(201, 202, 203) is achieved for TAnstMax just like at beginning ofcontrol 201 t0. This guarantees that the pump will achieve the necessarydelivery rate under high load, such as negative μ-deviation, poordelivery path, or a high admission pressure. Alternatively, a timeTAnstMaxA, which differs from TAnstMax, can be used, as illustrated inthe portion of FIG. 2 marked by dotted lines. Time difference t8−t7 isagain determined by sampling time dT. At the end of TAnstMax t9, pumpmotor 100 is again disconnected from supply voltage Ubat 204.

According to a further advantageous arrangement of the embodiment,various selected fixed periods TAnstMax and TAnstMaxA, respectively, areused for full drive at the beginning of control 201 TanstMax (t0, FIG.3), as well as for full drive upon reaching safety threshold Uss (t8,FIG. 3, e.g., TAnstMaxA). In addition, it can be useful to vary thesetting of full drive duration TAnstMax, based on certain values, e.g.,the pressure conditions in the break circuit, the pump motor speed,motor voltage UM, supply voltage Ubat, etc. The use of different periodsfor full drive is shown in the section of FIG. 2 marked by dashed lines.In this case, a time TAnstMax that differs from TAnstMax is used inblocks 201 a, 202 a, and 203 a. the functions of the individual blocksin the portion of FIG. 2 marked by dashed lines (201 a, 202 a, 203 a)are identical to blocks 201, 202, and 203 in FIG. 2, except for the useof TAnstMaxA. Like in 214/1, a check is carried out in block 214/4 todetermine whether the pumping request is still present. If not, the pumpis turned off in block 216 a and the event signaled to logic 109 a.

Instead of selecting fixed threshold values Us, Uss used in theembodiment, it would also be suitable, for example, to input variablevalues during the control operation, e.g., as a function of the pressureconditions in the brake circuit, the pump motor speed,. motor voltageUM, supply voltage Ubat, etc. In addition, the number of differentthreshold values used does not have to be limited to two. It isconceivable to use more than two or even only one threshold value,depending on the application.

In the case of a clocked driving action, it would also be advantageousto set this driving action not only to the single clock cycle TTakt usedhere. In a further embodiment, it would be advantageous to vary theclock cycle individually for each pumping request 200 in block 204 ofthe flow chart shown in FIG. 2, possibly as a function of certainparameters. The different clock cycles could even be assigned differentthreshold values.

According to the embodiment, beginning of control 201 takes place as aresponse to pumping request 200 from the superordinate logic. In theembodiment, for example, an anti-skid control system, friction controlsystem, and vehicle dynamics control system are used for this purpose.Other control systems are also conceivable. In an adaptive cruisecontrol (ACC) system, for example, a pumping request 200 does not haveto result in an intervention in the brake system. A situation in whichthe vehicle is in danger of running into the vehicle just ahead, andthus a fully intentional deceleration of the driver's own vehicle,triggers a pumping request 200. A pumping request 200, and thusbeginning of control 201, is therefore triggered by any desired changein pressure in the brake circuit, regardless of the control system used.

According to a further preferred configuration of the embodiment, FIG. 4also shows the above-mentioned refinements and improvements. The flowchart shown in FIG. 4 can be implemented entirely or partially byhardware; in addition, the illustrated flow chart can run on one or morecontrol units in the form of a program. Based on at least onesuperordinate logic, illustrated schematically by block 401, for examplean anti-skid control system, a traction control system, or a vehicledynamics control system. The illustrated methods can also be used in anysystem or control arrangement influencing the braking action to increasevehicle driving stability and/or safety. Superordinate logic 400provides quantities and variables for the subsequent sequence by defaultsettings, initialization, and/or calculation. These can includeoff-times for TPaus, various possible durations for TTakt, differentvoltage thresholds for Us1 and Us2, safety slow-down times for Tsn1-andTsn2, respectively, values for time thresholds Ts1, Ts2, TAnstMax, Ts,etc., time segments such as for dT1, and initial values, such as forTPstart. These values can be derived, for example, from estimates i.e.,model calculations, control- or system-specific settings or performancedata i.e., tables. Likewise, flags, i.e., identifying markers, can alsobe set and/or reset in the at least one superordinate logic, which isillustrated schematically as block 400, provided that this does not takeplace directly in the method itself. Furthermore, a pumping request fora control operation, in this case R1, R2, to initiate the processsequence, can also take place in block 400.

The process sequence begins in Field 401. Query 402 first performs acheck to see whether a control system, i.e., control strategy, is evenactive. This check can be carried out, for example with the help offlags, i.e., identifying markers, e.g., in the form or bits or bytes. Itis therefore conceivable for a system influencing the braking action,i.e., a control arrangement of this type for increasing vehicle drivingstability and/or safety, to set such a flag, or to cause such a flag tobe set, at the time this system is activated. Query 402 can also checkwhether a pump request from one of control systems R1 or R2 is present,which can also be indicated by setting flags. Thus, a flag F1P can showthat control system R1 (traction control in this case) has just issued apumping request, while a flag F2P can be used in the same manner forcontrol system R2.

By way of example, flags that are or have been set as a function ofcertain conditions are used in part in queries in the description below.

Of all the systems, i.e., control arrangements, influencing the brakingaction to increase vehicle driving stability and/or safety, two systems,R1 and R2, are used in this embodiment by way of example. This numbercan also obviously be increased to more than two control systems, i.e.,control strategies, and the use of only one strategy is also possible.For example, a traction control system is used for control system, i.e.,control strategy R1, while a anti-skid control system is used forcontrol strategy, i.e., control system R2.

Query 402 thus checks whether flag F1 is set for the traction controlsystem or flag 2 for the anti-skid control system, with these flagsindicating that at least one control system is active. If not, thesequence moves to the end of the program (441) via block 411.Initialization, default setting or possibly calculation of quantitiesand/or variables for the next loop pass can be carried out in block 411.

If at least one control system is active, query 403 checks whether bothcontrol systems R1 and R2, i.e., traction control and anti-skid control,are active simultaneously, i.e., whether an anti-lock brake system isused. If so, a subsequent query 404 determines which of the controlsystems, R1 or R2, must be accessing the pump. This is done, forexample, using a flag F1P which indicates that control system R1,friction control in this case, has performed a pump motor controloperation. If this flag F1P is set, the sequence goes on to query 406.If flag F1P is not set, the sequence goes on to query 405. Query 405 isalso reached from query 403 if control systems R1 and R2 are not bothactive. If an anti-lock brake system is therefore not used, the sequencemoves directly to the path beginning with query 405.

If query 403 determines that an anti-lock brake system is not beingused, i.e., that control systems R1 and R2 are not activesimultaneously, an additional query can conceivably determine which ofthe two control systems, R1 or R2 (traction control or anti-skidcontrol) is in use. On this basis, the path beginning with query 406 isthen selected for traction control or the path beginning with 405 foranti-skid control.

Query 406 performs a check for control system R1, traction control inthis case, to see whether a certain minimum drive time, i.e., minimumslow-down time Tsn of the pump, i.e., whether a counter for a minimumdriving time of this type, has a value greater than zero, indicatingwhether it is still present. This minimum slow-down time for controlsystem R1 (Tsn1) represents a kind of safety slow-down operation for thepump, for example if the loop pass is interrupted. This counter, i.e.,minimum drive time Tsn1, itself is decremented in block 408, i.e., atime segment dT1 is subtracted from Tsn1.

According to a preferred embodiment, time dT1 equals the time for oneloop pass in the flow chart, that is a count variable of 1. If the aimis to achieve real-time operation, it is conceivable to perform exactlyone loop pass per sampling step dT. In this case, dT wold then equaldT1. Otherwise, dT is less than dT1, i.e., more than one sampling stepper loop pass is carried out. This means that any quantity can be setfor dT1. This pump safety slow-down with minimum drive time Tsn alsoapplies to control system 2, in this case the anti-skid control system.Identical minimum pump drive time Tsn1 can be selected for safetyslow-down, or a time that differs from Tsn1 can be chosen with Tsn2.

Query 405 then also checks whether Tsn2 is greater than zero, whichmeans that minimum pump drive time Tsn2 has not yet ended. If minimumdrive time Tsn2, i.e., a counter variable assigned to it, is greaterthan zero, time segment dT1 is subtracted from minimum drive time Tsn(or Tsn2 in the case of R2, the anti-skid control system), i.e., acounter variable is decremented, in block 407 as well. Otherwise, a timesegment dT1 is not subtracted. Furthermore, the conditions that apply toTsn1 can be also used here.

Following the safety slow-down condition in query 406, the sequencepasses through block 408 to query 410. This query determines whether ornot full drive, for example identified by a flag Fvoll, should becarried out. This can be done in control system R1 (traction controlsystem), for example, by setting a flag Fvoll1 and checking whether itexists in query 410. Flag Fvoll1 can also be set as early as block 400,before a loop pass begins, due to the superordinate logic. It istherefore possible, depending on certain conditions, to perform fulldrive as a preventive measure even before a query of a voltage thresholdsuch as Us or Uss. Thus, before a situation of high load on the pumpactually occurs, this condition can be predicted as a function of atleast one condition and taken into account in advance, and thereforecontrolled, by increased pump operation, in particular by full drive.Previously, such a situation of high load could be detected and takeninto account only when motor voltage UM reached or dropped below avoltage threshold like Uss, i.e., only at the moment the situationoccurred.

To provide a preventive evaluation, a distinction can be made between aselect high mode (SH) and a select low mode (SL). Generally speaking,select high mode means that the braking action and/or driving stabilityand/or safety is controlled on the basis of the wheel on an axle wherethe highest coefficient of friction μ is detected, and at least thecontrol of the second wheel on the same axle is adjusted accordingly.Select low mode indicates the same thing, but based on the wheel on anaxle that demonstrates the lowest coefficient of friction μ.

Conditions that cause Fvoll, in particular Fvoll1, to be set include aone-sided control operation, such as select high mode SH and/or apreviously estimated wheel brake pressure RD that exceeds a selectablethreshold value of a pressure SD, for example between 60 and 80 bar, inparticular a buildup to a high wheel brake pressure level and/or apositive system deviation RA+, etc. This positive system deviationRA+occurs, for example, when a drive slip value of the wheel exceeds aselectable maximum valid slip threshold. Likewise, a tendency of a wheelto lock in an anti-skid control system can also produce a positivesystem deviation of this type. For example, all three above-mentionedconditions cause the flag, e.g., Fvoll1, to be set when combined intologic operation V1, i.e.,:

SH and RD>SD and RA+  (V1)

Wheel brake pressure RD can be estimated in advance, for example, byevaluating a characteristic curve or a characteristic map, which can bedetermined in advance by trials and/or simulation of standardsituations. An adaptive set of performance data that adjustscontinuously during operation and can be used to evaluate the pressureestimate, is advantageous. Another possibility is to use a pressureexerted during the previous loop pass to recursively determine thepressure to be achieved, in particular the wheel brake pressure, duringthe next loop pass. In addition to this recursive approach to estimatingpressure, a previously determined series of pressure drop and pressurerise pulses, respectively, can be used to establish how high thepressure, in particular the wheel brake pressure, is or will be during aspecific pressure pulse.

According to the conditions applying to select high mode SH, i.e.,select high control, used in V1, one wheel per axle is always beingcontrolled (one-sided control), in particular always only one drivewheel per driven axle. This is indicated, for example, by setting awheel control memory, i.e., a flag in this memory. In select high modeSH, therefore, traction control always takes place, e.g., adjusting to ahigh accelerative power in the case of the traction control system or toa short braking distance in the case of an anti-skid control system.

Likewise, useful conditions that set the Fvoll flag, in particularFvoll1, include a desired pressure drop from a high wheel brake pressurelevel (e.g., detected by at least one selectable pressure drop thresholdSDA exceeded by RD) and/or a two-sided control, in particular asimultaneous pressure drop at two wheels on the same axle, andconsequently a select low (SL) or select high mode (SH). In the case oftwo-sided control, both wheels on the same axle are thus controlled. Interms of the pressure drop thresholds (SDASH, e.g., 40-60 bar; SDASL,e.g., 15-35 bar), it is possible to distinguish between select high modeSH, with a select-high pressure drop threshold SDASH, and select lowmode SL with a select-low pressure drop threshold SDASL. If multiplewheels, in particular drive wheels, are controlled (two wheels instandard drive to four wheels in all-wheel drive), for example in selectlow mode SL, it is also possible to distinguish between each wheel(RD1-RD4) with respect to wheel brake pressure RD. For example, RD1 isthe estimated wheel brake pressure on the left side and RD2 the wheelbrake pressure on the right side of an axle, in particular a drivenaxle.

According to another conceivable preventive condition, it is possible toanalyze whether a pressure drop module (DABB module) or a pressure risemodule (DAUF module) is initialized and is or should be carried out,that is whether a pressure drop pulse series or a pressure rise pulseseries is or will become active to control the pump. A pressure moduleDM of this type, i.e., a DABB or DAUF module, especially in software, isinitialized before the actual pump operation. This is indicated by flagsDABB and DAUF, respectively, or generally by a flag D. If multiplewheels, especially drive wheels, are being controlled in this case aswell, a distinction can again be made between each wheel (DABB1-DABB4,DAUF1-DAUF4). In this case, for example, DABB1 corresponds to an activepressure drop module on the left side of a driven axle and DABB2 anactive pressure drop module on the right side.

Other preventive conditions can thus be derived from the descriptionabove in the form of logic operations for preventive pump control, forexample:

RD>SD and D  (V2)

or, specifically in the case of a pressure drop:

SH and RD>SDASH and DABB  (V3)

and

SL and RD>SDASL and DABB, respectively  (V4)

or in the case of a pressure drop in two-sided mode:

SL and RD 1 >SDASL and DABB 1 and RD 2>SDASL and DABB 2  (V5)

etc.

With respect to the conditions, select low mode SL, i.e., select lowcontrol, is characterized by conditions such as cornering, which result,for example, from the steering position. steering angle and/or atransverse acceleration sensor, and/or a higher velocity range (that isdetermined, for example, when a selectable velocity threshold value isexceeded, e.g., between 30 and 50 km/h), and/or for the respective drivewheels by setting one wheel control memory per wheel i.e., a flag ineach of these memories. Using flags also makes it possible to use onlyone wheel control memory for all drive wheels. In select low mode,therefore, control is aimed primarily at vehicle stability, for examplepreventing the vehicle from swerving and this taking into account alower accelerative power, e.g., in the case of the traction controlsystem, or a larger curve radius in the case of the vehicle dynamicscontrol system or a longer braking distance in the case of the anti-skidsystem. To rule out errors, select low mode can be assumed as non-selecthigh mode and vice-versa.

This situation, i.e., setting flag Fvoll1, therefore reveals a high loadon the pump. This is the case particularly in situations where the pumpmust reach a very high power output, in particular, its maximum poweroutput, for example when driving with a trailer or under μ-splitconditions such as μ-split on an incline approach. This enables controlsystem R1, i.e., the traction control strategy, to intervene in apossible, clocked pump motor drive via this flag Fvoll1 and switch thepump to full drive or continuous drive. Optionally, this would also bepossible for control system R2 (anti-skid control) via query 409.Similarly, a flag Fvoll2 can be set in this case, which, when present,activates full drive.

If flag Fvoll1 is set, the sequence moves on to block 415. There theduration of continuous drive or full drive, can be set, e.g., TAnstMaxor TAnstMaxA. In addition, the period of time when Fvoll1 is set andreset, respectively, can also be determined through these means. Inblock 415, therefore, pump off-time TPaus can be set to zero and periodTTakt to 1 or dTa. A flag FPTu is reset at the same time. Flag FPTu isset either during the process sequence or by a superordinate logic (seeblock 400) when a certain selectable period Tu after pump deactivationhas passed. As a result of this, a check to determine a voltagethreshold value, e.g., Us1, can thus be performed later on only within aselectable period Tu after pump deactivation. If flag Fvoll1 is not set,the sequence moves on to block 414. Here, a time threshold Ts is set toa specific value. This value corresponds to the drive time at thebeginning of control, for example, full drive period TAnstMax orTAnstMaxA, just like in the previous embodiment. As mentioned above, adesired full drive period Ts can also be set here as a function ofcertain conditions that may come from block 400. A TAnstMax1, forexample, having full drive time Ts, i.e., a corresponding timethreshold, is defined in this embodiment.

This definition is also possible as an option in block 413 for controlsystem R2 i.e., the anti-skid control system. A furthersituation-dependent value TAnstMax 2 adjusted to the specific controlsystem can be used for time threshold Ts in this case.

Also similarly to block 415 of control system R1 pump off-time TPaus canbe set to zero for full drive and period duration TTakt, for example,can be set to dT1, for a control system R2 in block 412. Likewise, aflag FPTu can conceivably be set. Query 409 and blocks 412 and 413 areoptional and can also be omitted, for example, for control system R2such as an anti-skid control system.

Blocks 412 to 415 lead to query 416. This query carries out a check tosee whether the time threshold preset in 413 or 414 has been reached inthe form of full drive time Ts, i.e., whether a pump start time TPstartis less than or equal to selectable time threshold Ts. If time thresholdTs has not yet been reached, start time TPstart is incremented by onetime segment dT1 in block 418. If a counter is used for start timeTPstart, the start time can be incremented by 1. The remarks made aboveapply. In addition, period duration TTakt is also set to a time segmentdT1, i.e., a loop pass, in block 418. Following block 418, the pump isactivated in block 439. A general full drive is therefore ensured at thebeginning of control with the query in block 416 and the subsequentactivation in block 439 if time threshold Ts is not reached.

If, however, pump start time TPstart does reach or exceed time thresholdTs, the sequence moves on to query 417. This query checks whetherselected period duration TTakt from either block 400 or in blocks 412and 415 has expired, for example by querying whether this time is equalto zero. If so, the sequence moves on to block 420, thus initiating aclocking operation. Period duration TTakt and off-time TPaus can beselected again in block 420. This setting can be made on the basis ofcalculations or estimates, i.e., pre-definitions, in superordinate logic400, or varied as a function of sampled values depending on thesituation. Selecting TTakt and TPaus also enables the pump on-time to beset with TTakt−TPaus=TPein, i.e., two of time quantities TTakt, TPaus,TPein generally determine the third one. The quantities that can be setare selectable.

If query 417 determines that period TTakt has not yet terminated, thesequence moves on to query 419. This query checks whether the sequenceis located within a short, selectable period of time Tu after pumpdeactivation. As mentioned above, this is done using flag FPTu. If flagFPTu is set, the sequence moves on to block 425 and is thus locatedwithin short selectable period of time Tu. If flag FPTu is not set, thesequence goes directly to query 432. This ensures that a first query ofa voltage threshold value Us1 can take place only within short period oftime Tu after pump deactivation. If set flag FPTu indicates that thesequence is within a short selectable period of time Tu after pumpdeactivation, a voltage threshold value Us1 is determined, i.e.,assigned, in block 425. This voltage value can be either fixed orvariable for each loop pass, as defined, for example by superordinatelogic 400. Set flag FPTu is simultaneously reset in block 425.

The sequence then moves on to query 426, which is comparable to query403. This query again checks whether both control systems, i.e., controlstrategies R1 and R2 in our example traction control and anti-skidcontrol, are active, i.e., whether an anti-lock brake system is present.If so, the sequence moves on to query 427, which, like query 404, nowchecks which control system, i.e., control strategy, is currentlydriving the pump motor. This can also be done, for example, with thehelp of a flag, e.g., with a flag F1P being set when control system R1(traction control in this case) is driving the pump motor. If this isthe case, a new voltage threshold value for Us1 can be defined in block429. This threshold value can now be either defined either as a fixedvalue, specifically for control system R1 or variable for each looppass. Either can be specified by superordinate logic 400. If query 426does not apply to a complete system composed of controller 1 andcontroller 2, the sequence moves from block 429 to query 430. Query 430now interrogates voltage threshold value Us1, which is defined either bya value from block 425 or a value from block 429. Both values can beidentical or be specific to the respective control strategies, andtherefore different. A comparison of motor voltage UM and voltagethreshold value Us1 now makes it possible to determine whether the pumpneeds to be turned on. Designation Us1 for the voltage threshold valueis arbitrarily selected; threshold value Us or Uss could also be used inthis case, based on the previous embodiment. This generally applies tothe designation of the voltage threshold value.

If motor voltage UM is not higher than threshold value Us1, or if it isequal to the latter, i.e., if it drops below threshold value Us1, thesequence moves on to block 431. Here time TPstart, i.e., a countercorresponding to this time, is reset to zero, i.e., to an initial value.This ensures that the pump motor receives full drive on the basis ofquery 416, which recurs in the next loop pass. This full drive ismaintained during the further loop passes until time threshold Ts isreached in query 416, and TPstart is incremented in block 418. BecauseTs can be selected in each loop pass using block 413 or 414, and theinitial value for TPstart can be selected in block 400, 411 or 431, avery specific drive period for full drive can be set. From block 432,the sequence returns to block 439, where the pump is turned on, i.e.,the pump motor is connected to the power supply. It is also conceivablefor full supply voltage Ubat not to be automatically applied to the pumpin block 439, but to set the voltage applied to the pump motor accordingto the needs of the situations or comparable conditions as a function ofthe control system (R1 or R2).

As mentioned above, the second path from query 417, i.e., when periodduration TTakt has expired, leads via block 420, where period durationTTakt and off-time TPaus can be selected once again. Period durationTTakt is decremented at the end of a pass, i.e., in blocks 439 and 440.As mentioned in connection with decrementing minimum slow-down time Tsn1and Tsn2, respectively, either a time segment dT1 or one loop pass issubtracted. Like with the remaining quantities, for example Us1, Ts,etc., period duration TTakt and off-time TPaus can also be permanentlyselected or varied according to the loop pass in the block concerned,for example by superordinate logic 400.

The sequence moves from block 420 to query 421, where a check is carriedout (like in query 403 or query 426) to see whether or not a completesystem is present, in our example, therefore, an anti-lock brake system.If so, the sequence moves on to query 422, which, like in query 427 and404, respectively, determines whether control system R1 is currentlydriving the pump motor, which is indicated, for example, by a set flagF1P, as mentioned above. If this is the case, the sequence moves on toblock 424, where another situation-dependent and control system-specificdefinition of period duration TTakt and off-time TPaus can be set forthis branch of the clocking operation. Likewise, flag FPTu, whichindicates that the end of clocking, i.e., the end of the period, hasbeen reached is also set in block 424.

If a complete anti-lock brake system composed of R1 and R2 is notpresent, the sequence moves from query 421 to query 432, just like fromblock 424. Query 432 is also reached from query 430 if the latterdetermines that motor voltage UM has not dropped below referencethreshold Us1. Query 432 then checks whether pump off-time TPaus has notyet been reached. This can occur, for example, by checking to seewhether TPaus, or a corresponding counter, is or is not equal to zero.If the counter or time TPaus is not equal to zero, the pump off-time hasbeen reached and the sequence returns to block 439 to activate the pump.If, however, TPaus is equal to zero, i.e., preset off-time TPaus has notyet been reached, the sequence moves on to block 433. Here, off timeTpaus, i.e., a corresponding counter, is decremented. This is done, forexample, either by decrementing or subtracting above-mentioned time unitdT1 per loop pass. In addition, a threshold value Us2 can be againselected in block 433. This value can be equal to or different fromprevious Us1. In this case, Us1 and Us2 are variables for voltagethresholds to which values can be assigned in the above-mentionedblocks, for example from model calculations, tables, or characteristicmaps.

The sequence moves from block 433 to query 434. This is again comparableto queries 403, 426, and 421 and determines whether a complete systemexists. If control system R1 and control system R2 are active, ananti-lock brake system is present, and the sequence moves on to query435, where a check is carried out to determine which control system isdriving the pump, just like in queries 427, 422, and 404. If the pump isbeing driven, for example, by control system R1 i.e., the tractioncontrol system, a control system- and situation-specific thresholdvoltage is again defined for Us2 in block 436. If, however, controlsystem R2 is actively driving the pump, i.e., if the anti-skid controlsystem is not driving the pump motor, the threshold voltage defined forUs2 in block 433 is used again.

The sequence moves to query 438 from query 434 if a complete system isnot present, from query 435 if control system R1 is inactive, and fromblock 436. Here, another comparison with a voltage threshold, this timewith Us2, is carried out, generally by clocking, i.e., if the safetythreshold for the voltage Us1 is not reached in query 430. If motorvoltage UM does not drop below the reference threshold value of Us2, thesequence moves on to block 440, where the pump is deactivated and periodduration TTakt is decremented. To do this, either period duration TTaktis reduced by subtracting time unit dT1 or a counter corresponding tothis period duration is decremented by one during each loop pass.However, if the voltage does drop below voltage threshold Us2, thesequence moves directly to block 439, thereby activating the pump.Period duration TTakt is decremented in the case as well. The sequencethen returns from block 439 or 440 to the beginning of the processsequence, where another check is carried out in query 402 to determinewhether the control system is still active. This means that at least oneof what in this case are two possible control systems R1 or R2 isactive.

With this method, and thus generally at the beginning of a controloperation, the pump is continuously driven for a selectable period oftime, e.g., TAnstMax, TAnstMaxA. At the end of this time, pump motorclocking begins with a freely selectable period duration TTakt,depending on the situation and in a manner specific to the controlsystem. The period begins with pump deactivation. Off-time TPaus itselfcan also be selected. Likewise, an on-time TPein can be selected insteadof TPaus, as mentioned above.

Pump motor voltage UM is calculated in each sampling step dT, forexample every 10 milliseconds, e.g., by analog/digital conversion in thecontrol unit, and is available to the process sequence. This isadvantageous if the maximum cycle time lies between the analog/digitalconversion and the output of control signal UP of the pump motor. Thisenables instantaneous pump motor voltage UM to respond immediately topump activation or deactivation, during the next cycle, since thisvoltage immediately reflects the pump load status.

If pump motor voltage UM drops to a value that is less than a voltagethreshold Us1, e.g., a safety threshold voltage Uss, immediately afterpump deactivation, i.e., during the next cycle, the pump is reactivatedfor a selectable period of time. This drop in pump motor voltage UMimmediately after deactivation indicates a heavy load on the pump duringthis phase. Consequently, the pump can be driven for a period that ismuch longer than period duration TTakt during this phase. This criticalthreshold Us1 can simultaneously serve to prevent the pump motor fromremaining at a standstill.

If pump motor voltage UM drops to a value that is less than a furtherthreshold voltage Us2, which can also correspond to safety threshold Us1or another threshold voltage Us, during normal clocking, the pump isreactivated for the rest of period TTakt.

In this embodiment, the pump motor drive is designed so that pumpdriving by a control strategy R1 traction control in our example, isindependent of drive operations by other control strategy R2 anti-skidcontrol in our example. This can be supported by various parameters andvarious logic components. Each control strategy, i.e., each controlsystem R1 or R2 (anti-skid control or traction control) can thusintervene in the pump motor clocking operation at any time, e.g., via aflag (Pvoll1 and Pvoll2, respectively, in the above example), dependingon the settings. Priority control procedures can avoid additional pumpdriving conflicts. In the above example, both flags can be set, forexample, to allow or deny access to the pump by the traction controlsystem. This makes it possible to intervene in the pump motor clockingoperation at any time, thus switching the pump to continuous or fulldrive, respectively. A modular layout of a pump motor control module canthus be provided in which only one algorithm, i.e., only one basiclogic, is used. This module enables independent pump motor clocking ofthe individual systems, i.e., control arrangements, influencing thebraking action for vehicle driving stability and/or safety to be usedsimultaneously.

The different selectable periods for pump activation and deactivationmake it possible to reduce the pump motor speed without sacrificingperformance.

Further advantages are obtained by reducing the pump motor current andconsequently in dimensioning the pump motor, since it needs to be drivencontinuously only for a short period of time. The period of full drivecan be limited by estimated wheel brake pressures (block 400),especially when reducing the pressure from a high wheel brake pressurelevel.

A pump motor module can be provided with an additional input for a flag,e.g., Fvoll1. Controlled by control system 1, i.e., by the tractioncontrol algorithm, this flag Fvoll1 can immediately suppress clockingfor driving the pump, and the pump can be driven in a different mode. Ofcourse, this also applies to all systems, i.e., control arrangements,influencing the braking action (anti-skid control, vehicle dynamicscontrol, etc.) to ensure vehicle driving stability and/or safety.

The above-mentioned embodiments and the conditions they provide can beused to adjust pump driving selectively and according to the pumpingrequest and the mode of operation.

Furthermore, the pump driving method is not limited to hydraulic brakesystems. Similarly, it could conceivably be used, for example, inelectro-hydraulic, pneumatic, electro-pneumatic, and other similar brakesystems.

Different methods for driving a pump in a brake system are provided inthe embodiment according to the independent claims by introducing aminimum pump on-time TPeinMin according to the present invention, whichcan also be used for exclusively clocked control of the pump.

What is claimed is:
 1. A method for driving a pump of a brake system,comprising: receiving by the pump, in response to a pumping request, atleast one control signal, the at least one control signal being constantover at least one time interval, being specifiable, and being formedfrom a sum of a pulse time and interpulse period of a duty cycle;initially connecting the pump to a voltage supply for a specifiable timeperiod; after initially connecting the pump and during the duty cycle,energizing the pump for a specifiable time period as a function of atleast one condition; and stopping the duty cycle for a specifiableperiod of time, the at least one condition being preventively evaluatedbefore the pump is loaded; wherein the at least one condition is anindex for an increased pump load in comparison with a pump load in dutycycle mode.
 2. A method for driving a pump of a brake system,comprising: receiving by the pump, in response to a pumping request, atleast one control signal, the at least one control signal being constantover at least one time interval, being specifiable, and being formedfrom a sum of a pulse time and interpulse period of a duty cycle;initially connecting the pump to a voltage supply for a specifiable timeperiod; after initially connecting the pump and during the duty cycle,energizing the pump for a specifiable time period as a function of atleast one condition; and stopping the duty cycle for a specifiableperiod of time, the at least one condition being preventively evaluatedbefore the pump is loaded; wherein the stopping step includes stoppingthe duty cycle by eliminating the interpulse period.
 3. A method fordriving a pump of a brake system, comprising: receiving by the pump, inresponse to a pumping request, at least one control signal, the at leastone control signal being constant over at least one time interval, beingspecifiable, and being formed from a sum of a pulse time and interpulseperiod of a duty cycle; initially connecting the pump to a voltagesupply for a specifiable time period; after initially connecting thepump and during the duty cycle, energizing the pump for a specifiabletime period as a function of at least one condition; and stopping theduty cycle for a specifiable period of time, the at least one conditionbeing preventively evaluated before the pump is loaded; wherein at leastone of: i) the at least one condition is selected from a plurality ofconditions, and ii) at least one arbitrary logic operation is formed asa condition from the plurality of conditions; wherein a logic operationfrom at least: i) at least one estimated pressure quantity exceeding atleast one pressure threshold, and ii) initializing a pressure module, isevaluated as a condition.
 4. A method for driving a pump of a brakesystem, comprising: receiving by the pump, in response to a pumpingrequest, at least one control signal, the at least one control signalbeing constant over at least one time interval, being specifiable, andbeing formed from a sum of a pulse time and interpulse period of a dutycycle; initially connecting the pump to a voltage supply for aspecifiable time period; after initially connecting the pump and duringthe duty cycle, energizing the pump for a specifiable time period as afunction of at least one condition; and stopping the duty cycle for aspecifiable period of time, the at least one condition beingpreventively evaluated before the pump is loaded; wherein at least oneof: i) the at least one condition is selected from a plurality ofconditions, and ii) at least one arbitrary logic operation is formed asa condition from the plurality of conditions; wherein a logic operationfrom at least: i) at least one estimated pressure quantity exceeding atleast one pressure threshold, and ii) a positive system deviation, isevaluated as a condition.
 5. A method for driving a pump of a brakesystem, comprising: receiving by the pump, in response to a pumpingrequest, at least one control signal, the at least one control signalbeing constant over at least one time interval, being specifiable, andbeing formed from a sum of a pulse time and interpulse period of a dutycycle; initially connecting the pump to a voltage supply for aspecifiable time period; after initially connecting the pump and duringthe duty cycle, energizing the pump for a specifiable time period as afunction of at least one condition; and stopping the duty cycle for aspecifiable period of time, the at least one condition beingpreventively evaluated before the pump is loaded; wherein at least oneof: i) the at least one condition is selected from a plurality ofconditions, and ii) at least one arbitrary logic operation is formed asa condition from the plurality of conditions; wherein a logic operationfrom at least: i) recognizing a unilateral control, and ii) at least oneestimated pressure quantity exceeding at least one pressure threshold,is evaluated as a condition.
 6. A method for driving a pump of a brakesystem, comprising: receiving by the pump, in response to a pumpingrequest, at least one control signal, the at least one control signalbeing constant over at least one time interval, being specifiable, andbeing formed from a sum of a pulse time and interpulse period of a dutycycle; initially connecting the pump to a voltage supply for aspecifiable time period; after initially connecting the pump and duringthe duty cycle, energizing the pump for a specifiable time period as afunction of at least one condition; and stopping the duty cycle for aspecifiable period of time, the at least one condition beingpreventively evaluated before the pump is loaded; wherein at least oneof: i) the at least one condition is selected from a plurality ofconditions, and ii) at least one arbitrary logic operation is formed asa condition from the plurality of conditions; wherein a logic operationfrom at least: i) recognizing a bilateral control, and ii) at least oneestimated pressure quantity exceeding at least one pressure threshold,is evaluated as a condition.
 7. A method for driving a pump of a brakesystem, comprising: receiving by the pump, in response to a pumpingrequest, at least one control signal, the at least one control signalbeing constant over at least one time interval, being specifiable, andbeing formed from a sum of a pulse time and interpulse period of a dutycycle; initially connecting the pump to a voltage supply for aspecifiable time period; after initially connecting the pump and duringthe duty cycle, energizing the pump for a specifiable time period as afunction of at least one condition; stopping the duty cycle for aspecifiable period of time, the at least one condition beingpreventively evaluated before the pump is loaded; and selecting amaximum pump break time per drive period to ensure a minimum pumprunning time per elementary drive period.
 8. A method for driving a pumpof a brake system, comprising: receiving by the pump, in response to apumping request, at least one control signal, the at least one controlsignal being constant over at least one time interval, beingspecifiable, and being formed from a sum of a pulse time and interpulseperiod of a duty cycle; initially connecting the pump to a voltagesupply for a specifiable time period; after initially connecting thepump and during the duty cycle, energizing the pump for a specifiabletime period as a function of at least one condition; stopping the dutycycle for a specifiable period of time, the at least one condition beingpreventively evaluated before the pump is loaded; and testing a voltagethreshold in a definite time interval as a condition of the at least onecondition, the pump being energized for the specifiable time period inresponse to the voltage threshold being reached.